Gas shielded arc welding



March 22, 1960 A. LESNEWICH 2,929,912

GAS smawsn ARC wswmc Original Filed April 29, 1954 3 Sheets-Sheet 1 IALEXANDER LESNEWICH FIG.

BY MW-7w,

ATTORNEY & AGENT March 22, 1960 A. LESNEWICH GAS SHIELDED ARC WELDING 3SheetLs-Sheet 2 Original Filed April 29 1954 INVENTOR. ALEXANDERLESNEWICH BY Hum M l ATTORNEY 8. AGENT March 22, 1960 A1 LESNEWICH2,929,912

GAS SHIELDED ARC WELDING Original Filed April 29, 1954 3 Sheets-Sheet 3FIG, 4

2a 1 r l FIG.6

INVENTOR. ALEXANDER LESNEWICH BY album M l 6w ATTORNEY & AGENT.

United States Patent 2,929,912 GAS SHIELDED ARC WELDING AlexanderLesuewich, New Providence, NJ., assignor to Air Reduction CompanyIncorporated, New York, N.Y., a corporation of New York Originalapplication April 29, 1954, Serial No. 426,388, now Patent No.2,859,329, dated November 1958. ;)ivided and this application August 6,1958, Serial No.

3 Claims. (Cl. 219-74) This invention relates to gas shielded arcwelding. More specifically it relates to gas shielded arc welding withmultiple shielding gas streams. This application is a division ofcopending application Serial No. 426,388, filed April 29, 1954, nowPatent No. 2,859,329 issued November 4, 1958.

Inert gas shielded arc welding with both consuming and non-consumingelectrodes is an important and useful welding method and for manywelding applications it has become substantially indispensable. Becauseof its assets the process is enjoying wide popularity despite the factit employs relatively expensive inert gas as the shielding medium.

An object of this invention is to provide improvements in methods andapparatus utilizing multiple shielding gas streams for elfecting asaving in the cost of shielding gas for gas shielded electric arcwelding.

Another object is to provide improvements in methods and apparatus forobtaining the arc characteristics of one shielding atmosphere with theshield forming characteristics of another shielding atmosphere.

A further object is to provide a novel method for forming an improvedmultiple gas stream encompassing a welding arc, wherein an outer annularshielding gas stream isolates an inner arc sustaining gas from theambient atmosphere, and to provide a novel type of noule constructionfor the projection of a plurality of laminar flow inert gas streamsabout a welding arc.

Another object is to provide improved methods and apparatus for gasshielded metal arc welding of metals, particularly of ferrous metals,with a welding are having the characteristics of the argon and/or heliumshielded are but with a gas shield composed predominantly of carbondioxide.

Another object is to provide improved methods and apparatus for gasshielded metal arc welding of metals, particularly copper base metals,with a welding arc having the characteristics of the argon and/or heliumshielded are but with a gas shield composed predominantly of nitrogen.

These and other objects and advantages of the invention will be pointedout or will become apparent from the following description and theaccompanying drawings. In general this invention contemplatesimprovements in arc welding with a plurality of shielding gas streamscooperating to form a novel composite shield having advantageousproperties and low. cost.

Fig. 1 illustrates generally suitable apparatus for the presentinvention.

Fig. 2 illustrates, partially in section and to a larger scale, thelower portion of the welding head shown in Fig. 1.

Fig. 3 illustrates, partially in section and to a larger scale, theupper portion of the .welding head shown in Fig. 1.

Fig. 4 is a plan view of the welding head of Fig. l drawn to the samescale as the sectional views of Figs. 2 and 3.

Fig. 5 is a partial elevational view of the upper portion of the weldinghead. The partial section shown in Fig. 5 is taken along line 5-5 ofFig. 4.

Fig. 6 is a section of the welding head taken along line 6-6 of Fig. 5.

Fig. 7 illustrates, schematically the gas flow patterns contemplated bythe present invention.

In inert gas shielded metal arc welding of the type disclosed in Mulleret al. Patent No. 2,504,868, a continuous bare electrode is fed downthrough an inert gas shield to a welding arc to effect a weld. It hasbeen found that this process depends, in part, for its success on theformation and maintenance of an adequate gas shield. The inert gas mustbe fed to the region of the arc as a nonturbulent flow stream. Thepresence of turbulence entrains air which adversely affects theelectrical characteristics of the arc and the metal transfercharacteristics across the arc and causes the formation of oxides andnitrides as well as porosity, in the weld metal. The shielding gasstreams, therefore, must be substantially non-turbulent and ofsufficient thickness and stiffness to retain its flow characteristicsfor an appreciable time (distance) as it is projected from the gasnozzle. It has been found that concentric annular streams of shieldinggas can be so projected from a properly formed nozzle at appropriatepressures and velocities, as to retain their individual identities for asufficient time to enable them to act separately, and at the same timecooperatively, to provide new and useful results in gas shielded arcwelding.

According to the present invention, a small diameter stream of amonatomic inert gas such as argon and/or helium is projected at a lowrate of flow from an inner nozzle to form an arc environment or areatmosphere through which a welding arc is maintained between anelectrode and a workpiece. Such inner arc sustaining gas streamdeliberately is made of such small diameter and low rate of flow as tobe incapable in itself of perfectly or completely shielding the arc andweld metal, thus, only a minimum amount of such inert gas is used. Thisthin inner shield would not per se be adequate to produce good weldingresults because it lacks sufiicient stiffness and thickness. If it wereprojected into the open air, its nonturbulent flow characteristics woulddeteriorate prematurely causing entrainment of air and resulting damageto the weld. However, a second or outer shielding gas stream, of acheaper gas such as carbon dioxide is projected around the said thininner shield so as to protect it from the open or ambient air. The outerstream confines the central or inner gas stream and causes it to retainits non-turbulent flow characteristics for a sufficiently long time(projected distance) to enable this small diameter inner gas stream toelfectively provide the required shielding atmosphere for the arc. Therate of flow of the inner stream, is made sufiiciently large relative tothe rate of flow of the outer stream that when this inner stream strikesa flat plate held at right angles to the axis of the stream the gasspreads out in all directions (as may be observed by smoke tracer testsin the absence of the arc) to form a smoothly flowing film of inert gasover the weld and the surrounding surfaces of the plate. When the flowrates of the two streams are properly regulated the outer retainingshield spreads out above the film of gas produced by the inner gasstream and under ideal conditions, the outer gas is separated from thesurgas streams consequently are merged into a single, laminated, flowingcolumn having an inner core encompassed down through the welding by anouter annulus, prior to their discharge into the open air.

Thus welding according to the Muller et al. process can be p fonued w tha mu h l e flo of monatom ne h ldia l as i n oute aux i y t m of gas isprojected around a central shielding strearn to confine it and preventits flow characteristics from deteriorating. This surrounding gas streamcan be composed of a relatively inexpensive gas, and thus, the net costof welding by the Muller et al. process can be substantially reduced. Asa practical matter it occasionally is difficult to prevent any mixing ofthe two gas streams. It is always possible however, to substantiallycompletely prevent mixing of the gas streams in the region of the arcprior to impingement of the streams on the work surface. Further, if theo g e a p operly sel te n re t on to e h he and to the metal beingWelded some mixing may be tolerated and can even in some instances, bebeneficial. For example, carbon dioxide has been found to be anexcellent gas for projection as an annular shielding stream around aninner arc sustaining core of argon, particularly for the welding offerrous metals with the inert gas shielded consumable electrode process.Similarly, nitrogen is considered as suitable for retaining or isolatingan inner core of argon, particularly for the welding of copper.

Referring to Fig. 1 a workpiece to be welded is designated 20. A weldinghead 21 is illustrated as supported in operable relation to theworkpiece by any conventional means. Relative motion is provided betweenthe workpiece and the welding head by the motorized carriage 22. Thewelding apparatus illustrated is, in general, of the type disclosed andclaimed in Muller et a1. Patent 2,504,868. It comprises a reelcontaining a continuous length of electrode wire and means forwithdrawing this wire and feeding it through the welding head to theweld zone where an electric arc is maintained from the electrode wire tothe work. The wire reel 23 is mounted on a carriage frame 24 whichhouses a wire feed motor and associated wire feeding apparatusdesignated generally as r 25. Wire is withdrawn from the reel 23 by thewire feeding mechanism 25 and pushed through a flexible casing 26 to thewelding head 21. Welding current is supplied from a welding machine 27through the welding cable 28 to the welding head 21. A ground lead 29connected from the workpiece to the welding machine 27 completes thewelding circuit. Shielding gas is provided from compressed gas cylinders31 and 32 through the usual pressure and flow control apparatus to theWelding head 21 by tubes 33 and 34. The welding head 21 may be cooled bycirculating water supplied to the head by tube 35 and dischargingthrough tube 36.

Figs. 2, 3, 4, 5 and 6 illustrate the construction of the welding headin greater detail. Basicady the welding head comprises a Welding currentcontact tube 37 which is electrically connected through the internalmetal parts of the welding head to the welding cable 28. The electrodewire W, fed to the welding head through casing 26, passes head whichincludes the contact tube 37. Welding current is transferred to theelectrode wire from the contact tube 3'7. The welding arc is maintainedfrom the end of wire W to the workpiece 20.

The welding head includes concentric barrels 38 and 39 which formconcentric annular gas passages 46 and 41 surrounding the welding headwire guide and contact tube assembly 42. Shielding gas is supplied fromcylinder 31 through hose 33 into annular passage 41. Shielding gas issupplied from cylinder 32 through hose 34 into annular passage 40.Annular passages '40 and 41 provide relatively long unobstructedapproach passages to their respective discharge orifices, Diffusers 46and 47 in the respective passages assist in the formation of anon-turbulent gas flow through the passages andaid in maintaining theconccntricity of the assembly. The cooling water is. cir- 4 culatedthrough the length of the wire guide assembly by cooling water passages48, 49. The outer gas nozzle is separately water cooled by circulatingwater in annular passage 50.

It has been found advantageous, according to the present invention, totaper inwardly the nozzle forming extremities of both the inner andouter barrels as clearly indicated in the drawing. This gradual andcontrolled reduction in cross sectional area through which the gasstream must pass seems to increase the velocity without adverselyaffecting the non-turbulent flow characteristics and thereby makespossible the projection of the stream with non-turbulent characteristicsa considerable distance. even through the volumetric fiow is relativelysmall. Also because of the practical necessity of getting so many partsin concentric relation to one another in a duplex nozzle device, the useof straight untapered nozzles would mean having the outer nozzleparticularly, of relatively large diameter. By terminating the innerbarrel upstream from the outer barrel, a further necking-down or a wiredrawing effect is produced in the inner gas stream further increasingits stiffness despite the relatively low how and without disturbing thelaminar flow characteristics of either stream.

By terminating the inner barrel upstream from the outer barrel thepressure equalization between the two gas streams and the atmosphere isaccomplished in two stages which further lessens the possibilities ofintroducing turbulence into the streams. V

An example of good design practice in a welding head of this type forelectrode wires up to /8 inch diameter is as follows:

Outside diameter of water cooled wire guide and con- 7 tact tubeassembly 42 /2 inch.

Inside diameter of inner barrel 38-% inch.

Outside diameter of inner barrel 3%% inch.

Inside diameter of outer barrel 39- 1 A inches.

Angle of taper of terminal portion or nozzle of outer barrel 39-30"total included angle (15 angle with axis of barrel). 7

Length of tapered portion of barrel 39 (measured along axis)l inch.

Outer barrel discharge orifice diameter-% inch.

Angle of taper of terminal portion or nozzle of inner barrel 3830 totalincluded angle (15 angle with axis 01' barrel).

Length of tapered portion of barrel 33 (measured along axis)% inch.Inner barrel discharge orifice diameterinch.

Axial distance from. discharge face of outer barrel to discharge face ofinner barrel-7s inch.

Axial distance from discharge face of outer barrel to end of Wire guideand contact tube assembly-V4 inch.

This invention has been found particularly useful and economical in theWelding of carbon and low alloy steels. It has been found for example,that good welds can be made using a welding head as described above withargon as the central gas stream delivered at a flow rate of only 12cubic feet per-hour. For thewelding of carbon steels, low alloy steels,and nickel, CO has been found highly satisfactory as the outer gasstream. it is heavy and a relatively low flow of the order of 40 cubicfeet per hour adequately retains the inner shield and prevents thedeterioration of its flow characteristics. it is advantageous to use aheavy or dense gas to form the outer shield because such gases providegood shield forming character.- istics. C0 is only slightly reactivewith steel and contact of the CO with the molten weld metal is notdetrimental. Since CO is believed to break down to CO and O in theelectric arc, slight mixing of the CO with the argon has the effect ofadding small quantities of 0-,; to the argon. This has been foundbeneficial in steel welding. With apparatus as described, welding withargon and CO on steel produces the beneficial results that derive fromthe Muller et al. process but the cost of shielding gas has been greatlyreduced. With conventional welding heads flow rates of 50 cubic feet perhour of argon might be required for a given welding job. At a rate ofper cubic foot shielding gas per hour of welding (assuming a continuousduty cycle) amounts to $5.00. With the present invention the sameresults can be obtained using 12 cubic feet of argon at 10 per cubicfoot and 40 cubic feet per hour of CO: at 95 per cubic foot. Using theduplex shield, the total gas cost per hour is only $1.40.

It has been found that good results can be obtained with a welding headof the type described above under the following gas flow conditions:

Flow of CO: Flow of A through outer through inner annulus. c,i,h,annulus. c,i,h,

In each of the above cited examples the optimum argon flow was about /3of the C0 fiow. For the apparatus described above it was also found thatgood results were obtained (argon arc electrical characteristics andargon are metal transfer characteristics with adequate shielding of theweld puddle) if the ratio of the velocity of the gas flow in the outerannulus to the velocity of the gas flow in the inner annulus is between.75 and 2.00. It was also observed that good results were accompanied bya ratio of the Reynolds number for the flow of CO in the outer annulusto the Reynolds number for the fiow of A in the inner annulus of lessthan 6. The inner gas shield flow rate must be suflicient to prevent theinward radial flow of gas from the outer shield stream toward the are asa result of impingement of the streams on the work.

As may be expected the exact nozzle configuration described above is notthe only operable design. It was found, for instance, in fillet weldingthat it was advantageous to modify the outer barrel nozzle geometrysomewhat. In one instance it was made longer and tapered down to a inchorifice with good results. In another instance this nozzle was made ovalin cross section at the orifice.

While the application of this invention to the welding of carbon steelsand low alloy steels using CO, and argon as the shielding gases has beenfound most advantageous, the same principle and reasoning can be appliedto the welding of other materials, or to the welding of the samematerial with other gases. For instance, steel can readily be weldedwith helium as the inner shield and CO; as the outer shield. Also, ofcourse, mixtures of helium and argon or mixtures of an inert gas withminor percentages of active gases can be employed as the inner shield.Nickel can also be welded with an inert gas inner shield and a C0 outershield. For the welding of copper and high copper alloys, an inert gasmay be used as the inner shield and nitrogen, which is relatively inertwith respect to copper, may be used as the outer shield.

While this invention has been described with respect to inert gasshielded consuming electrode arc welding, the principles are equallyapplicable to inert gas shielded nonconsuming electrode arc welding.

Although only certain specific embodiments of the invention have beenshown and described herein in connection with gas shielded arc weldingwith multiple shielding gas streams, it is to be understood that theinvention is not limited to the particular forms, disclosed, but may beused in other ways without departure from its spirit as defined by thefollowing claims.

I claim:

1. A method of gas shielded arc welding which comprises establishing andmaintaining an electric welding are between an electrode selected fromthe group comprising copper and copper alloys, and a workpiece,surrounding said arc with a shielding gas stream comprising essentiallyinert monatomic gas projected as a non-turbulent flow stream, andconfining said arc surrounding stream with a non-turbulent flow streamcomprising essentially nitrogen.

2. A method of gas shielded arc welding non-ferrous metals whichcomprises establishing and maintaining an electric welding are between anon-ferrous electrode and a workpiece, surrounding said arc with ashielding gas stream comprising essentially monatomic inert gas, andconfining said arc surrounding stream with a stream comprisingessentially nitrogen.

3. A method of gas shielded electric arc welding comprising establishingan electric welding are between an electrode and a workpiece, envelopingsaid are with a flowing stream of gas comprising essentially monatomicinert gas, and incapable in itself of adequately shielding the terminalportion of said electrode, said are, and the molten weld metal producedthereby, and supplementing said arc enveloping stream with a surroundingannular stream of gas comprising essentially nitrogen which acts toconfine said are enveloping stream and produce therewith an adequateshield for said electrode, said are, and the molten weld metal producedthereby.

References Cited in the file of this patent UNITED STATES PATENTS2,522,482 Olzak Sept. 12, 1950 2,681,970 Koopman June 22, 1954 2,758,186Ludwig Aug. 7, 1956 2,859,329 Lesnewich Nov. 4, 1958 FOREIGN PATENTS297,911 Switzerland June 16, 1954 770,351 Great Britain Dec. 21, 1954

1. A METHOD OF GAS SHIELDED ARC WELDING WHICH COMPRISES ESTABLISHING ANDMAINTAINING AN ELECTRIC WELDING ARC BETWEEN AN ELECTRODE SELECTED FROMTHE GROUP COMPRISING COPPER AND COPPER ALLOYS, AND A WORKPIECE,SURROUNDING SAILD ARC WITH A SHIELDING GAS STREAM COMPRISING ESSENTIALLYINERT MONATOMIC GAS PROJECTED AS A NON-TURBULENT FLOW STREAM, ANDCONFINING SAILD ARE SURROUNDING STREAM WITH A NON-TURBULENT FLOW STREAMCOMPRISING ESSENTIALLY NITROGEN.